Electro-acoustic system and method



Feb. 11, 1958 R. H. RINES ELECTRO-ACOUSTIC SYSTEM AND METHOD OriginalFiled July 18, 1945 I INVENTOR F062 Fines ATTORNEY 5 United States P wnELECTRO-ACOUSTIC SYSTEM AND METHOD Robert Harvey Rines, Newton, Mass.

Original application July 18, 1945, Serial No. 605,722, now: Patent No.2,539,593, dated January 30, 1951. Divided and this application January22, 1951, Serial No. 207,200

21 Claims. (Cl. 340-6) The present invention relates to the transmissionand reception of intelligence, using both sound and electromagneticenergy as the agencies of communication, and more particularly to meansemploying the directive discrimination of sound beams. The term soundwill be employed hereinafter, in the specification and the claims, toinclude the ultrasonic, as well as the audible, part of the soundspectrum, and to include also all kinds of elastic vibrations. Theinvention, indeed, finds particular application to high-frequency sonicor ultrasonic communication or detection. The present application is adivision of copending parent application, Serial No. 605,722, filed July18, 1945, now Patent 2,539,593, for Electro-Acoustic System.

An object of the invention is to provide a new and improvedcombined-sound-and-electromagnetic system and method for communicationand detection.

A further object is to provide a novelbuoy for communicatingintelligence or signals detected under the water from a source of soundvibration by means of electromagnetic energy.

Still another object of the invention is to provide a new and improvedsystem for submarine detection.

An additionalobject is toprovide a novel corner reflector system adaptedto modulate radio waves reflected therefrom in accordance with acousticvibrations impinged upon the system.

Other and further. objects will be explained hereinafter and will beparticularly pointed out in the appended claims.

The invention will now be more fully explained in connection with theaccompanying drawing, the single figure of which is a diagrammatic viewof circuits and apparatus embodying the invention in preferred form.

As explained in the said parent application, and in U. S. Letters Patent2,063,944, issued December 15, 1936,

to' George W. Pierce, a transversely vibratory conduct.

ing element, such as a diaphragm, when disposed in a sound-conductingmedium at an angle to a beam of sound waves, may be set into transverseharmonic, as well as fundamental, modes of vibration. With the diaphragmorientedat the Pierce angle 0, the sound beam in the medium strikes allvibratory regions in the diaphragm in the proper phase to enhance thevibration, producing spacial resonance between the diaphragm and thevibrations in the medium. As the diaphragm thus occupies a given anglecorresponding to resonant response to the sound beam, it is possible todetermine the direction of the sound beam, and as departure from theangle associated with resonance carries with it nonresonance, itispossible to obtain a very sharp determi nation of direction of the soundbeam.

The diaphragm Or other vibratory element may, as explained in the saidparent application, and in said Letters Patent, be used either fortransmitting a sound beam directionally in a predetermined direction orfor receiving asound beam from a predetermnied direction. If thediaphragm is oriented at the Pierce angle 6 with respect to the planewave front of, for example, received sound waves, the following relationobtains:

comprise a first pair of diverging plates, wings or plane diaphragmsurfaces 22 and 24, rigidly connected together into a single mechanicalunit. As illustrated, for example, in Fig. 13 of the said Letters Patent2,063,944, these two plates may be in the form of a dihedral angledegrees minus 20, so as to provide a single forwarddirectedmulti-diaphragm unit, driven by the sound waves received from an objectsuch as an under-water submarine 37. The plates or wings 22 and 24 areshown as rigid continuations of a second pair of diverging conductingplates, wings or plane diaphragm surfaces, 12 and 14, respectively,though they may, if desired, be electromagnetically insulated from theseplates 12 and 14 as shown at 18 and-20. The insulators 18 and 20,however, are capable of conducting elastic vibrations from the diaphragmplates 22 and 24 into the respective diaphragm plates 12 and 14.

The conducting surfaces 12 and 14 constitute an electromagnetic-wavecorner reflector, and they are positioned in the air above the surfaceof the water 43 to permit their use with radio waves. The plates 22 and24 may be submerged below the surface 43 of the water, as before stated,in order that they may serve, for example, as detectors of soundvibration emitted by or reflected and scattered from the submarine 37.The system 2224, 12-14, is shown supported by a buoy hereinafterdescribed.

In the angle between the surfaces 12 and 14 of the corner reflector,there is shown positioned a radio antenna 10, illustrated as a dipolethat may be excited from a radio-frequency oscillator 2 supported in asealed container 8 forming the upper portion of the buoy. This systemmay be balanced in the water by a weight 39 about a vertically disposedshaft 40, driven by a self-powered motor 42 disposed in a sealed box 38connected with the box 8. The buoy may be held in place in the water byanchors 44.

As disclosed in the said parent application, when a conducting elementadapted to support radio-frequency energy is transversely vibrated, asin response to elastic vibrations of predetermined frequency to whichthe conducting means is preferably of sufficient dimensions to respondby producing mechanical resonance, the radiofrequency energy transmittedor received by the conducting means will be found to be modulated by theelastic vibrations produced therein.

In the preferred system illustrated in the drawing, therefore, if thevibratory plates or wings 22 and 24 are of sufiicient dimension torespond mechanicallyto strong frequency components emitted from orotherwise emanating from the submarine 37, when the plates 22 and 24 aredisposed to face the submarine or other source of sound waves, such thatthe bisector of the angle between the plates 22 and 24 is pointing inthe direction of the source, the plates or wings 22, 24 will be set intotransverse mechanical vibration. These vibrations. will.be

transferredthrough the elements 18 and 20, if employed,

Patented Feb. 11, 1958 to the wings 12 and 14 above the surface of thewater 43. The dimensions of the plates or wings 12 and 1,4 arepreferably also such that they, too, are thereupon set into transversemechanical vibration. The frequency of the radio-frequency energyemitted by the dipole and reflected from the plates 12 and 14 isadjusted such that the plates 12 and 14 have appropriate dimensions togive a satisfactory directional radio-beam property to theradio-frequency energy.

In the case illustrated, radio waves are emitted from the antenna system10, 12, 14, and beamed directionally into space. The antenna 10 ispreferably positioned along the bisector of the dihedral angle, and at adistance from the vertex axis of the plates 12, 14 approximately equalto a quarter of the radio-frequency wavelength employed. These radioWaves will be modulated, as before stated, in accordance with thetransverse mechanical resonant vibration of the plates 2224 and 12-14 atthe time that the system 2224, 1214 is pointing directly at the sourceof the underwater sound vibration, such as the submarine 37. Aradio-receiving station (not shown) in the air oriented along thisdirection, would then receive the radio signals carrying this modulationand would then be informed of the presence and the direction of thesubmarine 37. Inasmuch as the degree of modulation produced is dependentupon the amount of vibration set up in these plates, an indication maybe had of the approximate range of the submarine 37 from the buoy by thedegree of modulation received at the radio-receiving station.

The complete diaphragm unit 2224, 12-14 may be continuously rotatedabout the vertically disposed shaft 40 by the motor 42, periodically toreceive sound vibrations from submarines or other sources in alldirections of azimuth, and simultaneously to transmit through the air,along the corresponding directions, a radio beam modulated by thereceived sound waves. If desired, the plates 12, 14 may be twisted at anangle with respect to the plates 22, 24, thereby to effect transmissionof the radio beam along a different direction from the reception of thesound beams. The modulated radio signals may be received, as beforestated, at suitably located receiving stations (not shown) on shore, inthe air, or on the sea, as on light ships.

This system is useful even without the antenna 10 and its excitingmechanism 2. Radio pulses or other radio energy may be transmitted from,for example, an aircraft radar or any other transmitting station, to thecorner reflector 12, 14, so as to be reflected therefrom. The aircraftor other station would then receive the reflected waves as modulated bythe sound waves coming from the submarine at the time the system pointsin the direction of the submarine. In this manner a completely passivesystem is provided.

By using radio-frequency oscillators 2 of different frequencies withdifferent buoys, moreover, it is possible to determine which buoy isissuing a particular modulated signal. This may be desired where thebuoys are to maintain fixed orientations and are not to be rotated toscan in azimuth.

As disclosed in the said parent application, systems of this charactermay be used also completely in air. Where the system of the presentinvention is utilized completely in air, as to detect acousticvibrations in the air and to modulate the reflected radio waves inaccordance therewith, both the pair of elements 12-14 and the pair ofelements 2224 act not only as acoustic devices but also as radio-wavecorner reflectors. Periodic rotation of such reflectors would, ofcourse, indicate the directions in which acoustic vibrations werereceived, as before discussed.

While the system illustrated and described has been thus far discussedin connection with receiving sound vibrations, such as under-watervibrations, as further explained in the said parent application, and inthe said Letters Patent, the diaphragms 22, 24 may, if desired, bedriven as by magnetostrictive cores (not shown) directionally totransmit sound beams into the water. The radio waves reflected from theupper wings 12, 14 will then also, of course, be modulated by theelastic vibrations set up therein as a result of the vibration of thewings 22, 24.

It is to be understood, moreover, that'while radio-wave reflectingsurfaces in the form of the dihedral or corner reflectors and soundvibration-responsive dihedral-angle surfaces 22, 24 have beenillustrated, other configurations are also possible. As disclosed in thesaid parent application, plane reflecting surfaces may, as anotherillustration, be utilized, or surfaces having any desired curvature maysimilarly be employed. Instead of these surfaces taking the form ofplanar sheets or plates, moreover, as explained in the said parentapplication, they may, if desired, assume the form of thin strips orrods or any other configuration. In the latter case, they may, indeed,be omni-directionally responsive to both or either of the sound wavesand the radio waves. In all cases, however, one vibratory portion of thesystem is to be inserted into the water 43 or other medium in which thesound waves are to be transmitted or received. Another portion which mayinclude or even be the same as the said one portion where the medium isair, is utilized for the propagation of radio waves either by directexcitation from a radiofrequency generator or by reflectedradio-frequency energy, the radio waves being modulated in accordancewith the vibrations.

Further modifications will occur to persons skilled in the art, and allsuch are considered to fall within the spirit and scope of the inventionas defined in the appended claims.

What is claimed is:

l. Apparatus of the character described that comprises means fordirectionally receiving sound waves under water, means for transmittingradio signals responsive to the received sound waves, means forconfining the transmission of the radio signals along substantially onedirection only having a fixed relation to the direction from which thesoundwaves are received, and means for periodically changing thedirection of reception of the sound waves.

2. Apparatus for indicating the presence of submarines that comprisesmeans for directionally receiving sound Waves under water from thesubmarine, means for directionally transmitting radio signals modulatedby the received sound waves, and means for confining the directionaltransmission of the radio signals along a direction. having a fixedrelation to the direction from which the sound waves are received.

3. An electro-acoustic system having a directional acoustic receiveradapted to be positioned below the surface of the water to receive soundwaves below the surface of the water, means for transmittingelectromagnetic waves through the air modulated by the received soundWaves, and means for confining the transmission of the electromagneticwaves to substantially one direction only having a fixed relation to thedirection of reception of the sound waves.

4. An electro-acoustic system having radio-wave conducting meansdisposed in a first medium for transmitting radio waves, an acousticreceiver disposed in a second medium adapted to vibrate in response tosound waves impinging upon it, and means mechanically connecting theacoustic receiver to the radio-wave conducting means to cause thevibrations of the acoustic receiver to vibrate the radio-Wave conductingmeans in order to modulate the radio waves transmitted by the radio-waveconducting means.

5. An electro-acoustic system having radio-wave conducting means fortransmitting radio waves, an acoustic receiver adapted to vibrate inresponse to sound waves impinging upon it, the acoustic receiver beingadapted to be positioned below the surface of the Water to receive soundwaves from an object below the surface of the water, and meansconnecting the acoustic receiver to the antenna to carry the vibrationsof the acoustic receiver to the radio-wave conducting means in order tovibrate the radio-wave conducting means thereby to modulate the radiowaves transmitted by the radio-wave conducting means.

6. An electro-acoustic system having, in combination, a buoy forfloating upon the surface of a body of water, a first conducting meanssupported by the buoy below the surface of the water, the firstconducting means being mechanically vibratory in response to soundvibrations directed thereupon, a second conducting means supported bythe buoy above the surface of the water to transmit radio waves abovethe surface of the water, and means mechanically connecting the firstand second conducting means for transmitting mechanical vibrations ofthe first conducting means produced in response to the directing ofsound Waves thereupon to the second conducting means, therebymechanically to vibrate the second conducting means in order to modulatethe radio waves transmitted by the second conducting means in accordancewith the sound vibrations of the first conducting means.

7. An electro-acoustic system of the character described in claim 6 andin which the first conducting means comprises means for directionallyreceiving sound vibrations.

8. An electro-acoustic system of the character described in claim 6 andin which the second conducting means directionally transmits radiowaves.

9. An electro-acoustic system of the character described in claim 6 andin which the first conducting means comprises means for directionallyreceiving sound vibrations and the second conducting means directionallytransmits radio waves.

10. An electro-acoustic system of the character describedin claim 6 andin which the first conducting means comprises a dihedral-angle diaphragmsystem.

11. An electro-acoustic system of the character described in claim 6 andin which the second conducting means comprises a directional reflectingsystem.

12. An electro-acoustic system of the character described in claim 6 andin which the second conducting means comprises a corner reflector.

13. An electro-acoustic system of the character described in claim 6 andin which the first conducting means is provided with a planar surface.

14. An electro-acoustic system having, in combination, a plurality ofelectromagnetic wave reflectors forming diverging reflecting surfacesfor directionally transmitting electromagnetic waves, the surfacesbeing'vibratory in response to acoustic vibrations, and means forperiodically rotating the reflectors as a unit.

15. An electro-acoustic system having an electromagnetic wave reflectorprovided with a pair of diverging reflecting surfaces for directionallytransmitting electromagnetic waves, a surface of the reflector beingtransversely vibratory in response to acoustic vibrations in order tomodulate the transmitted electromagnetic waves in accordance with theacoustic vibrations, vibratory means for directionally receiving soundwaves and cansing the said reflector surface to vibrate acoustically inunison therewith in response to the received sound waves, and means forrotating the reflector to transmit the 6 modulated electromagnetic wavesalong predetermined directions.

16. An electro-acoustic system having, in combination, anelectromagnetic-Wave reflector provided with a pair of divergingreflecting surfaces for directionally transmitting electromagneticwaves, vibratory means for receiving sound waves and causing transversevibration of the reflector to propagate elastic vibrations therealong inunison with the vibration of the vibratory means in order to modulatethe transmitted electromagnetic waves in response to the vibrations.

17. An electro-acoustic system having, in combination, anelectromagnetic-wave reflector provided with a pair of divergingreflecting surfaces for directionally transmitting electromagneticWaves, and vibratory means for receiving sound waves and causingtransverse vibration of the reflector surfaces to propagate elasticvibrations therealong in unison with the vibration of the vibratorymeans in order to modulate the transmitted electromagnetic wavesinresponse to the vibrations.

18. An electro-acoustic system having, in combination, anelectromagnetic-wave corner reflector provided with a pair of divergingreflecting surfaces for directionally transmitting electromagnetic wavesimpinging from a remote source of electromagnetic waves upon thereflecting surfaces, a portion of the reflector being transverselyvibratory in response to acoustic vibrations in the medium surroundingthe said portion to vibrate the reflector in unison with the vibrationof the said portion in order to modulate the transmitted electromagneticwaves in accordance with the acoustic vibrations.

19. An electro-acoustic system of the character described in claim 16and in which the said reflector surfaces are each angularly disposableat an angle to the direction of the said sound waves such that the saidelastic vibrations propagated along the reflector surfaces shall have avelocity component, in the said direction, substantially equal to thevelocity of the sound waves as they are received.

20. An electro-acoustic system of the character described in claim 18and in which the said portion of the reflector comprises one of the saidreflector surfaces.

21. An electro-acoustic system having, in combination, a radio Wavereflector provided with a pair of diverging radio Wave reflectingsurfaces of dimensions appropriate for directionally transmitting radiowaves impinging from a radio-wave source upon the reflecting surfaces,at least a portion of the reflector being transversely vibratory inresponse to sound vibrations in the medium surrounding the said portionto vibrate the reflector in unison with the vibration of the saidportion in order to modulate the transmitted radio waves in accordancewith the sound vibrations.

References Cited in the file of this patent UNITED STATES PATENTS2,063,944 Pierce Dec. 15, 1936 2,431,018 Bailey Nov. 18, 1947 2,432,984Budenbom Dec. 23, 1947 2,448,787 Ferrel Sept. 7, 1948 2,461,005Southworth Feb. 8, 1949 FOREIGN PATENTS 405,613 Great Britain Jan. 26,1934 596,439 Germany May 3, 1934

